Television receiver circuit



I June 20, 1939. SCHLESlNGER 2,163,217

TELEVISION RECEIVER CIRCUIT Filed Dec. 50, 1955 IWIMWHI WW F Patented June 20, 1939 UNITED STATES PATENT OFFICE TELEVISION RECEIVER CIRCUIT Steglitz, Germany Application December 30, 1935, Serial No. 56,755 In Germany January 2, 1935 8 Claims.

The present invention relates to television receivers and more particularly to detecting and associated arrangements for use therein.

In the patent application Ser. No. 747,011 there has been described a rectifying circuit, in which a freely oscillating grid coil tuned to the intermediate waves only by the inherent capacities is connectedwith two control grids which, not twisted one within the other, are arranged opposite the common earthed cathode, and the carrier-frequency amplifications of which compensate each other by phase opposition in the anode circuit. An object of the present invention is to obtain the same result with a more simple arrangement. In accordance with the invention there is provided a push-pull diode rectifier with subsequent amplifying system and the connection between rectifying and amplifying system is performed galvanically. The received carrier wave modulated with television signals is applied to the detector means in a reverse phase circuit and the demodulated television signals are taken from a point of said circuit which is arranged to be substantially at zero potential as regards oscillations of carrier wave frequency. For amplifying purposes there is employed a normal triode or screening grid tube or penthode. A twin-grid arrangement may then be dispensed with.

In the present case the different electrode systems preferably use the same cathode in the same tube. But if different bias is applied to the single systems the single cathode coatings of the heating element are insulated from each other, for example in Fig. 1 there is shown a cathode, the heating element of which has three single coatings 5', 5", and 5".

Two embodiments of the invention will now be described, by way of example only, with reference to the drawing left with the provisional specification in which:

Fig. 1 shows a circuit arrangement and valve construction suitable for use in a television receiver for detecting carrier waves modulated with television signals, amplifying the demodulated signals and then separating the synchronising impulses from the image signals.

Fig. 2 shows a modification of the arrangement of Fig. 1.

In Fig. 1, I is the secondary coil of an intermediate frequency transformer which is coupled to the primary coil 2, which is connected to the final stage of the intermediate frequency amplifier. The adjustment of this coupling may be effected by one of the methods described in the application Ser. No. 751,927 and Ser. No.

748,644, e. g. by diplacing coil I relatively to coil 2 until the outer ends of the secondary coil I oscillate at reverse phase with reference to the earthed cathode 5. The coil is damped by means of a resistance 6. The two outer ends of the coil I are connected to anodes 3 and 4 of low capacity which operate in conjunction with cathode 5' to form a push-pull diode detector. The incoming oscillations are thus coupled by the transformer coils I, 2 to the rectifying system. When the adjustment of the coils has been correctly eiTected so that the outer ends of coil I are at reverse phase potential, the mid-point of coil I is free from carrier frequency potential and a demodulated potential containing only the image frequencies is formed across a high ohmic resistance 1 which is connected between earth and the mid-point of coil I (or the mid-point of resistance 6). This potential is supplied to control grid 8 of an amplifier system which may be in a separate envelope but is preferably in the same envelope as the detector system (as shown) and is arranged over the same cathode 5' or a part-cathode 5" insulated from 5' heated by the same heater as cathode 5. The amplifier system comprises at least an anode 9, grid 8 and cathode 5" and may further comprise a screen of suppressor grid I6. Anode 9 is connected to a source of positive potential via resistance I 0. The feed current in this circuit containing resistance ID may be adjusted by applying a suitable grid bias to screen grid I6 from bias battery II. When employing a triode this can be effected by altering the potential of anode 9. In the case where the amplifier has a separate part-cathode 5", this problem can be solved by giving the part-cathode 5" a suitable bias from a battery II.

The same valve, by the addition or a further electrode system as shown in Fig. 1, may also be used to effect the amplitude separation of the synchronising impulses from the image signals. For this purpose a further cathode 5" is provided which is insulated from cathode 5" but still heated by the same heater. Grid 8 of the amplifier system is extended in the form of an anode ring 8' over the cathode 5". Cathode 5" is given a weak'negative bias from battery I2 with the result that the supply conductor to the cathode 5" is in general without current and that current only flows in this conductor when the carrier wave is interrupted by a synchronising impulse. When this occurs, the potential of the upper end or resistance I becomes zero, that is, has its highest positive value, a weak current flows from cathode 5" through resistance [3 thus causing the right-hand end of resistance I 3 to become more positive. The positive potential variations across resistance [3 are filtered by means of the known capacity/resistance and resistance/capacity filters as shown in Fig. 1 so that short positive line synchronising impulses appear at terminal I 4 and long positive image synchronising impulses appear at terminal I4' Alternatively the synchronisation may be effected in the manner shown in Fig. 2. In this case, the anode 9 of the amplifier system is connected directly to cathode 5" and the auxiliary anode 8 arranged over the latter is led out through the envelope of the valve. Anode 8' is supplied with a positive potential from battery I2 via the primary windings of transformers l5 and I5 and conductor M. The rectifying and amplifying electrode-systems use the same common earthed cathode 5. In the arrangement of Fig. 2 the rectified oscillations are taken from a centre tap at damping resistance 6*. From this centre tap the rectified impulses are led via operating resistance 1 to earth, the potential drop across this resistance is operative at grid 8 of the amplifier system.

When the carrier wave is interrupted, current flows from battery I2 to anode 8 so that negative impulses are produced at conductor l4. Transformers l5 and I5 which are tuned to the line andimage synchronizing frequency respectively are so arranged that the necessary positive strikingimpulses are obtained at terminals I4 and I 4". On account of the amplified potential applied to cathode 5 from anode 9, the discriminating power of the amplitude filter of Fig. 2 is slightly greater than of Fig. 1.

I claim:

1. A' television circuit arrangement for receiving carrier oscillations modulated with a frequency mixture containing picture contents frequencies and synchronising frequencies comprising an input circuit with a transformer having a primary and a secondary coil, a double diode system for demodulating the carrier oscillations, an electrode-system for amplifying the demodulated frequencies, an electronic filtering system for filtering the synchronizing frequencies from the modulated frequency mixture and an output circuit, said double diode system having two plates and a cathode, said carrier oscillations being applied to said transformer, from the secondary of which the oscillations are led in push-pull fashion to the plates of said diode system, said electrode-system for amplifying the demodulated frequencies having at least an anode, a cathode and a control grid, said control grid being directly connected to a centre tap of said secondary coil which is damped by a parallel resistance, said electronic filtering system having a plate and a cathode being directly connected to'the amplifying electrode system,

said amplifying electrode system and said filtering system being connected with the output circuit from which the picture signals and the synchronising signals respectively are taken.

2. A television circuit arrangement for receiving carrier oscillations modulated with a frequency mixture containing picture contents frequencies and synchronising frequencies comprising an input circuit with a transformer having a primary and a secondary coil, a double diode system for demodulating the carrier oscillations, an electrode-system for amplifying the demodulated frequencies, an electronic filtering system for filtering the synchronizing frequencies from the modulated frequency mixture and an output circuit, said double diode system having two plates and acathode, said carrier oscillations being applied tosaid transformer, from the secondary of which the oscillations are led in push-pull fashion to the plates of said diode system, said electrode-system for amplifying the demodulated frequencies having at least an anode, a cathode and a control grid, said conrol grid being directly connected to a centre tap. of said secondary coil which is damped by a parallel resistance said electronic filtering system having a plate and a cathode being directly connected to the amplifying electrode system, said amplifying electrode system and said filtering system being connected with the output circuit from which the picture signals and the synchronizing signals respectively are taken, said three electrode-systems for rectifying, amplifying and synchronising being arranged in the same envelope.

3. A television circuit arrangement for receiving carrier oscillations modulated with a frequency mixture containing picture contents frequencies and synchronising frequencies comprising an input circuit with a transformer having a primary and a secondary coil, a double diode system for demodulating the carrier oscillations, an electrode-system for amplifying the demodulated frequencies, an electronic filtering system for filtering the synchronising frequencies from the modulated frequency mixture and an output circuit, said double diode system having two plates and a cathode, said carrier oscillations being applied to said transformer, from the secondary of which'the oscillations are led in pushpullfashion to the plates of said diode system, said electrode-system for amplifying the demodulated frequencies having at least an anode, a cathode and a control grid, said control grid being directly connected to a centre tap of said secondary'coil which is damped by a parallel resistance, the centre-tap being simultaneously connected to earth by means of an operating resistance, said electronic filtering system having a plate and a cathode being directly connected to the amplifying electrode system, said amplifying electrode system and said filtering system being connected with the output circuit from which the picture signals and the synchronising signals respectively are taken, said three electrode-systems for rectifying, amplifying and synchronising being arranged in the same envelope.

4. A television circuit arrangement for receiving carrier oscillations modulated with a frequency mixture containing picture contents frequencies and synchronising frequencies comprising an input circuit with a transformer having a primary and a secondary coil, a double diode system for demodulating the carrier oscillations, an electrode-system for amplifying the demodulated frequencies, an electronic filtering system for filtering the synchronising frequencies from the modulated frequency mixture and an output circuit, said double idode system having two plates and a cathode, said carrier oscillations being applied to said transformer, from the secondary of which the oscillations are led in pushpull fashion to the plates of said diode system, said electrode-system for amplifying the demodulated frequencies having at least an anode, a cathode and a control grid, said secondary which is connected to said diode plates being damped by a parallel resistance which has a centre tap to which the control grid of said amplifying system is directly connected and which centre tap is simultaneously connected to earth by means of an operating resistance, said electronic filtering system having a plate and a cathode being directly connected to the amplifying electrode system, said amplifying electrode system and said filtering system being connected with the output circuit from which the picture signals and the synchronising signals respectively are taken.

5. An arrangement according to claim 1 wherein the cathodes of said three electrodessystems are heated by the same common heating element, isolated from one another and supplied with a suitable bias.

6. An arrangement according to claim 1 wherein the cathodes of said three electrodessystems are heated by the same common heating element, and rectifier and amplifier systems have the same common cathode whilst the oathode of said filtering electrodes-systems is isolated from said other cathode, both cathodes being supplied with a suitable bias.

7. An arrangement according to claim 1 wherein the control grid of said amplifier electrodes-system projects through the dischargespace of said amplifier-system, said projecting part being used as anode for said filtering systerm.

8. An arrangement according to claim 1 wherein the anode of said amplifier system is directly connected to the cathode of said filtering system.

KURT SCI-ILESINGER. 

